We propose to study the development and disorder after injury of the inputs to the superior colliculus. Particular attention is being given to the development of the uncrossed optic pathway in the rat to attempt to find the mechanism whereby a major part of this pathway is suppressed during development. Further work is directed at the parabigeminal input to the rat's superior colliculus as a way of testing the interaction between it and the retinal and cortical afferents, especially when one is injured. These studies, besides providing specific information important for understanding the development of the visual system and its response to injury, also define systems in which general questions important in consideration of the development and plasticity of the nervous system can be answered.